disable sync folder for CI

[evgeni]

No description provided.

[ekohl]

I thought it was weird that Rubocop passes on Ruby 3.1, but not on older versions. Then I saw this:

forklift/vagrant/Gemfile

Lines 14 to 18 in 0753db1

	if RUBY_VERSION < '3.1'
	# we need a rubocop that still can manage Ruby 2.0 code
	# but 0.49.x is not compatible with Ruby 3.1
	gem 'rubocop', '<0.50'
	end